Centrifugal fan

ABSTRACT

Disclosed herein is a centrifugal fan. The centrifugal fan includes a back plate having a central portion for coupling with a rotation center shaft, a plurality of blades extending from the back plate, and a shroud which is connected to end portions of the blades and has an introduction end portion and a discharge end portion through which fluid passes, and the discharge end portion is rounded with a predetermined curvature in a direction away from the back plate.

TECHNICAL FIELD

The present invention relates to a centrifugal fan, and more particularly, to a centrifugal fan capable of maximizing efficiency of a diffuser to reduce flow noise.

BACKGROUND ART

In general, various blower fans for forcibly blowing gas are installed in home appliances such as an air conditioner or ventilation systems of factory equipment. Such blower fans may be classified into an axial fan and a centrifugal fan according to flow characteristics of blowing gas.

The axial fan is a blower fan in which gas flow is generated in parallel with a rotary shaft. The centrifugal fan is a blower fan in which gas flow at an inlet of each blade is generated in a direction of a rotary shaft but gas flow at an outlet of the blade is generated in a radial direction perpendicular to the rotary shaft.

The axial fan has a disadvantage that static pressure performance is very low due to a structure thereof. Thus, a size of the blade or a rotation speed of the fan should be increased in order to increase the static pressure performance in the axial fan.

However, in the case of home appliances such as an air cleaner, size increase of the products has a limitation. For this reason, increase of the static pressure performance in the axial fan mainly depends on the increase of the rotation speed of the fan, instead of increase of the size of the blade.

However, when the rotation speed of the fan is increased, there is a problem in that loud noise is generated due to increase in pressure waves between air and the blade.

Accordingly, when the axial flow is required and the size increase of the products is limited, products adopting the centrifugal fan having high static pressure performance, instead of the axial fan, are recently increased in order to resolve the disadvantages of the above axial fan.

Hereinafter, a conventional centrifugal fan 100 will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view illustrating an example of a circular compressor in which a bell mouth 200 is coupled to the conventional centrifugal fan 100.

The centrifugal fan 100 may be coupled to the bell mouth 200 which is arranged at an introduction side of fluid with respect to the centrifugal fan 100 and has an inner diameter that gradually decreases toward the centrifugal fan 100. The fluid introduced into the bell mouth may be guided in a direction of a rotation center shaft of the centrifugal fan 100 through a shroud 110 to be described later.

Meanwhile, the centrifugal fan 100 includes a back plate 130 having a central portion for coupling with the rotation center shaft. A plurality of blades 120, which aids in movement of the fluid and transfers energy to the fluid, is arranged at the back plate 130.

In addition, the centrifugal fan 100 may include the shroud 110 coupled to end portions of the blades 120. The shroud 110 defines a movement passage of the fluid together with the blades 120.

The centrifugal fan 100 may include a diffuser 140 for increasing a pressure of the fluid. The diffuser 140 serves to increase the pressure of the fluid by decreasing the speed of the fluid passing through the inside of the centrifugal fan 100.

In an example of the diffuser 140, the diffuser 140 may be formed at both tip ends of the shroud 110 and the back plate 130. As shown in FIG. 1, discharge end portions of the diffuser 140, namely, discharge end portions of the shroud 110 and back plate 130 through which the fluid is discharged, generally have a chamfered shape.

When the diffuser 140 has low efficiency, there is a problem in that a temperature of the fluid is abnormally increased by compression during change of the pressure.

In addition, since performance of the diffuser 140 is directly related to the compression performance of the compressor having the centrifugal fan 100, increase in efficiency of the diffuser 140 may be an important goal.

DISCLOSURE OF INVENTION Technical Problem

An object of the present invention devised to solve the problem is to provide a centrifugal fan including a diffuser capable of minimizing vortex generation.

Another object of the present invention devised to solve the problem is to provide a centrifugal fan capable of increasing efficiency of a diffuser by decreasing a vortex generated on a surface of a shroud to reduce torque of fluid.

A further object of the present invention devised to solve the problem is to provide a centrifugal fan capable of increasing efficiency of a diffuser so that abnormal temperature increase of fluid is prevented and compression performance of a compressor is increased.

Solution to Problem

The object of the present invention can be achieved by providing a centrifugal fan including a back plate having a central portion for coupling with a rotation center shaft, a plurality of blades extending from the back plate, and a shroud having a circular ring shape and connected to end portions of the blades.

The shroud may include an introduction end portion through which fluid is introduced, a connection portion curved to have a diameter that gradually increases from the introduction end portion, and a discharge end portion through which the fluid is discharged via the connection portion, and the discharge end portion may be rounded in a direction away from the back plate.

The discharge end portion of the shroud and a circumferential portion of the back plate may be rounded in opposite directions to each other.

The back plate may include a connection portion which extends in a radial direction of the back plate from the central portion and connects the central portion to a circumferential portion.

The discharge end portion of the shroud and the circumferential portion of the back plate may form a diffuser.

In this case, the circumferential portion may be rounded in a direction away from the discharge end portion of the shroud. That is, a distance between the discharge end portion of the shroud and the circumferential portion of the back plate may be gradually increased in a discharge direction of the fluid.

The central portion may protrude toward the introduction end portion. That is, the back plate may be continuously rounded from the central portion to the circumferential portion of the back plate.

The discharge end portion may have a larger curvature than the connection portion, and the curvature of the discharge end portion may be equal to or more than a single arc (1arc).

Advantageous Effects of Invention

In accordance with an embodiment of the present invention, it may be possible to provide a centrifugal fan capable of increasing efficiency of a diffuser by decreasing a vortex generated on a surface of a shroud to reduce torque of fluid.

In addition, it may be possible to provide the centrifugal fan capable of increasing the efficiency of the diffuser so that abnormal temperature increase of fluid is prevented and compression performance of a compressor is increased.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

In the drawings:

FIG. 1 is a cross-sectional view illustrating an example of a circular compressor in which a bell mouth is coupled to a conventional centrifugal fan;

FIG. 2 is a perspective view illustrating a centrifugal fan according to an exemplary embodiment of the present invention;

FIG. 3 is a cross-sectional view illustrating a circular compressor in which a bell mouth is coupled to the centrifugal fan according to the exemplary embodiment of the present invention;

FIG. 4 is an enlarged cross-sectional view illustrating both tip ends of a shroud according to the exemplary embodiment of the present invention;

FIGS. 5 and 6 are cross-sectional views illustrating a circular compressor including a centrifugal fan according to another exemplary embodiment of the present invention;

FIG. 7 is a table illustrating a comparison of efficiency of diffusers according to the related art and the exemplary embodiments of the present invention;

FIG. 8 is a graph illustrating P-Q performance measured according to the related art and the exemplary embodiments of the present invention; and

FIG. 9 is a graph illustrating the efficiency of the diffusers according to the related art and the exemplary embodiments of the present invention.

MODE FOR THE INVENTION

General terms which are currently and widely used are selected as the terminologies used in the present invention in consideration of functionality of the present invention, and may be changed depending on the user s intention or practice in the art, the appearance of new technologies, or the like. In addition, some terms have been arbitrarily selected by the applicant for special cases, for which detailed meanings are explained in detail in the description of the preferred embodiments of the present invention. Hence, the terminologies used in the present invention should be defined not as the names of the terminologies but as the meanings of the terminologies based on the entire content disclosed herein.

In the following embodiments, the components and features of the present invention are combined in a predetermined manner. Unless otherwise specified, each component or feature may be selectively considered. Each component or feature may be embodied in a form which is not combined with another component or feature. In addition, the embodiments of the present invention may also be configured by combination of partial components and/or features. A partial configuration or feature of any embodiment may be incorporated in other embodiments, or may be replaced with the corresponding configuration or feature of the other embodiments.

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

FIG. 2 is a perspective view illustrating a centrifugal fan 100 according to an exemplary embodiment of the present invention. A structure of the centrifugal fan 100 according to the exemplary embodiment of the present invention will be described with reference to FIG. 2.

The centrifugal fan 100 may include a back plate 130 having a central portion 131 for coupling with a rotation center shaft, and a plurality of blades 120 extending from the back plate 130. Each blade may extend such that an outer contour thereof is curved.

The blades 120 form rotary vanes of the centrifugal fan 100 and function to transfer kinetic energy of the centrifugal fan 100 to fluid. The plurality of blades 120 may be provided at predetermined intervals and radially arranged on the back plate 130.

In addition, the centrifugal fan 100 may include a shroud 110 coupled to end portions of the blades 120. The shroud 110 may be formed at a position facing the back plate 130, and have a circular ring shape.

The shroud 110 has an introduction end portion 111 through which the fluid is introduced, and a discharge end portion 113 through which the fluid is discharged. The shroud may be curved so as to have a diameter decreased toward the introduction end portion 111 from the discharge end portion 113.

That is, the shroud 110 may include a connection portion 112 which connects the introduction end portion 111 to the discharge end portion 113 in a curved form. The connection portion may have a curvature and be rounded such that an inside cross-sectional area of the shroud is enlarged.

The shroud 110 may define a movement passage of the fluid together with the back plate 130 and the blades 120.

With regard to a movement direction of the fluid, the fluid introduced in a direction of the center shaft may flow in a circumferential direction of the centrifugal fan 100 by rotation of the blades 120.

That is, the centrifugal fan 100 may discharge the fluid in a radial direction of the centrifugal fan 100 by increasing flow speed with centrifugal force.

In addition, the centrifugal fan 100 may include a diffuser 140 for converting kinetic energy of the fluid into pressure energy. The speed of the fluid is decreased while the fluid accelerated in the circumferential direction by rotation of the centrifugal fan 100 is diffused, and the kinetic energy of the fluid may be converted into an effective pressure.

In accordance with the embodiment of the present invention, the diffuser for increasing the pressure of the fluid may be formed by the shroud 110 and the back plate 130.

The shroud 110 coupled to the end portions of the blades 120 may be spaced apart from the back plate 130 by a predetermined distance. The shroud 110 has a surface which is parallel with and faces the back plate 130.

In this case, the diffuser 140 is formed between both tip ends of the shroud 110 and back plate 130. That is, the discharge end portion 113 of the shroud 110 through which the fluid is discharged and a circumferential portion 132 of the back plate may serve as a diffuser.

The efficiency of the diffuser may be measured by dividing the product of a pressure

P and a quantity of flow Q of fluid by the product of torque and revolutions per minute (RPM). When the efficiency of the diffuser 140 is decreased, a temperature of the fluid is abnormally increased by compression during change of the pressure.

In order to prevent the above problem and increase compressor performance, it is important to determine a structure and shape of the diffuser 140.

FIG. 3 is a cross-sectional view illustrating a circular compressor in which a bell mouth 200 is coupled to the centrifugal fan 100 according to the exemplary embodiment of the present invention. The centrifugal fan 100 is not limited to being applied to the above-mentioned embodiments, and the centrifugal fan 100 according to the present invention is applied as long as it may change pressures and speeds of fluid by rotation.

In accordance with the exemplary embodiment of the present invention provided to increase the efficiency of the diffuser, the discharge end portion 113 of the shroud 110 forming the diffuser may be rounded to have a predetermined curvature. In this case, the discharge end portion 113 of the shroud 110 is preferably rounded in a direction away from the back plate 130.

The tip end of the shroud or back plate according to the embodiment of the present invention will be described in more detail with reference to FIG. 4.

The curvature through which the discharge end portion of the shroud or the circumferential portion of the back plate is rounded may be provided such that a length L defined from a starting point of the rounded portion of the shroud 110 to the tip end of the shroud 100 and a height H of the shroud 110 are a single arc (1arc) or a double arc (2arc).

Particularly, the discharge end portion 113 may have a larger curvature than the connection portion 112. That is, the discharge end portion is preferably rounded with a larger curvature than the circumferential portion in the direction away from the back plate.

Another exemplary embodiment of the present invention will be described with reference to FIGS. 5 and 6. In the embodiment, a back plate 130 and a shroud 110 are both optimized in order to increase efficiency of a diffuser.

First, in the embodiment of the present invention shown in FIG. 5, both of a discharge end portion 113 of the shroud 110 and a circumferential portion 132 of the back plate 130 may have a curvature and are rounded.

That is, the circumferential portion 132 of the back plate 130 and the discharge end portion 113 of the shroud 110 may be rounded in opposite directions to each other.

Accordingly, it is preferable that a distance between the discharge end portion 113 of the shroud 110 and the circumferential portion 132 of the back plate 130 be gradually increased in a discharge direction of fluid.

In other words, since the circumferential portion 132 of the back plate 130 is rounded in an arc form, the distance between the shroud 110 and the back plate 130 is gradually increased toward both tip ends thereof.

Similarly to the case of the shroud 110, the curvature may be provided to be a single arc (1arc) or a double arc (2arc), but the present invention is not limited thereto.

Referring to FIG. 6, the back plate may be rounded to both ends from a central portion 131 which is the highest portion. That is, the central portion may protrude toward an introduction end portion 111. Thus, the back plate may be formed in a parabolic form extending from the central portion 131 of the back plate to the circumferential portion 132 thereof.

That is, the back plate is continuously rounded from the central portion 131 to the circumferential portion 132 thereof.

Accordingly, a distance between an imaginary line connecting the lowest points of the discharge end portion 113 of the shroud 110 and the back plate 130 is preferably the closest in the central portion 131 provided in the back plate 130.

This may mean that the distance between the shroud 110 and the back plate 130 is gradually increased toward the circumferential portion 132 from the central portion 131.

Hereinafter, variation in efficiency of the diffuser according to the exemplary embodiment of the present invention will be described in more detail with reference to FIGS. 7 to 9.

The diffuser 140 (hereinafter, referred to as OPT.1) of the embodiment in which the discharge end portion of the shroud 110 is rounded to have a predetermined curvature may improve efficiency by 0.57%, compared to the conventional diffuser 140 shown in FIG. 1 in which the discharge end of the diffuser 140 has the chamfered shape instead of having a curvature.

In addition, the diffuser (hereinafter, referred to as OPT.2) of the embodiment in which the central portion 131 of the back plate 130 protrudes toward the introduction end portion 111 may improve efficiency by 0.93%, compared to the conventional diffuser 140.

The diffuser (hereinafter, referred to as OPT.3) of the embodiment in which the circumferential portion 132 of the back plate 130 is rounded to have a predetermined curvature, similarly to the discharge end portion 113 of the shroud 110, improves efficiency by 0.99%.

That is, when both tip ends of the shroud 110 and back plate 130 forming the diffuser 140 are rounded to have the curvature, the diffuser may have the highest efficiency.

In addition, when the linear distance between the shroud 110 and the back plate 130 is provided so as to be increased at a certain ratio toward the circumferential portion 132 from the central portion 131, the efficiency of the diffuser may be increased.

The exemplary embodiments of the present invention described above have been designed to minimize a vortex generated by the diffuser 140. When vortex generation is reduced, torque of the fluid is decreased. When the torque is decreased under the same P-Q performance, the efficiency of the diffuser is increased.

The above-mentioned description will be given in more detail with reference to FIG. 8. P-Q static pressure curves of the OPT.1 and OPT.3 are little difference from that of the conventional diffuser 140. That is, the P-Q performance according to variations of the pressure and the quantity of flow may be almost identical even though the shapes of the shroud 110 and back plate 130 are changed.

However, the efficiency of the OPT.1 or the OPT.3 may be improved compared to that of the conventional diffuser 140, as shown in FIG. 9. The efficiency of the OPT.2 may also be significantly improved compared to that of the conventional diffuser 140, under the quantity of flow which is equal to or less than about 170 CMM.

Particularly, the OPT.3 may have the maximum efficiency. That is, when both of the shroud 110 and the back plate 130 are rounded with a predetermined curvature, the diffuser may have the highest efficiency.

The configuration and method of the above-mentioned centrifugal fan 100 are not limited to the above embodiments, and the entirety or a portion of each embodiment may be selectively combined such that various modifications may be made in the embodiments.

Various embodiments have been described in the best mode for carrying out the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A centrifugal fan comprising: a back plate having a central portion for coupling with a rotation center shaft; a plurality of blades extending from the back plate; and a shroud having a circular ring shape and connected to end portions of the blades, wherein the shroud comprises: an introduction end portion through which fluid is introduced; a connection portion curved to have a diameter that gradually increases from the introduction end portion; and a discharge end portion through which the fluid is discharged via the connection portion, and wherein the discharge end portion is rounded in a direction away from the back plate.
 2. The centrifugal fan according to claim 1, wherein the discharge end portion has a larger curvature than the connection portion.
 3. The centrifugal fan according to claim 2, wherein the curvature of the discharge end portion is equal to or more than a single arc (1arc).
 4. The centrifugal fan according to claim 1, wherein the back plate comprises a connection portion which extends in a radial direction of the back plate from the central portion and connects the central portion to a circumferential portion, and the circumferential portion is rounded in a direction away from the discharge end portion of the shroud.
 5. The centrifugal fan according to claim 4, wherein a distance between the discharge end portion of the shroud and the circumferential portion of the back plate is gradually increased in a discharge direction of the fluid.
 6. The centrifugal fan according to claim 4, wherein the discharge end portion of the shroud and the circumferential portion of the back plate form a diffuser.
 7. The centrifugal fan according to claim 1, wherein the central portion protrudes toward the introduction end portion.
 8. The centrifugal fan according to claim 7, wherein the back plate is continuously rounded from the central portion to the circumferential portion of the back plate.
 9. A centrifugal fan comprising: a back plate having a central portion for coupling with a rotation center shaft; a plurality of blades extending from the back plate; and a shroud having a circular ring shape and connected to end portions of the blades, wherein the shroud comprises: an introduction end portion through which fluid is introduced; a connection portion curved to have a diameter that gradually increases from the introduction end portion; and a discharge end portion through which the fluid is discharged via the connection portion, and wherein the discharge end portion of the shroud and a circumferential portion of the back plate are rounded in opposite directions to each other.
 10. The centrifugal fan according to claim 9, wherein the discharge end portion of the shroud and the circumferential portion of the back plate are rounded in directions away from each other.
 11. The centrifugal fan according to claim 9, wherein the central portion protrudes toward the introduction end portion.
 12. The centrifugal fan according to claim 9, wherein the back plate is continuously rounded from the central portion to the circumferential portion of the back plate. 